1. Field of the Invention
The present invention relates to a sliding material composition. In particular, the present invention relates to a sliding material composition comprising a polyphenylene sulfide resin, a melt processable fluorine-containing resin and polytetrafluoroethylene.
Such a composition provides a heat-resistant plastic sliding material which can be injection molded so as to improve productivity.
2. Description of the Related Art
Recently, a large amount of heat-resistant plastic materials have been used as materials of sliding parts such as a bearing. Many of such materials are compositions comprising a heat-resistant base resin in which powdery polytetrafluoroethylene (hereinafter referred to as "PTFE") or an inorganic solid lubricant,(e.g. molybdenum disulfide or graphite) is used as a filler in order to impart abrasion resistance or a lubricating property to the resin.
The abrasion resistance and lubricating properties which are imparted by the addition of PTFE most effectively contribute to a decrease in the friction coefficient. Then, PTFE is used as an additive filler to many heat-resistant resins.
As the base resin of the sliding material composition, polyphenylene sulfide (hereinafter referred to as "PPS") is widely used because of its good heat resistance, stiffness, moldability, chemical resistance, etc. A composition of PPS to which PTFE is added to impart abrasion resistance and the sliding property is widely used as a heat-resistant material (see Japanese Patent Kokai Publication No. 73275/1977).
However, the addition of only the solid lubricants including PTFE cannot sufficiently improve abrasion characteristics, and the PPS composition containing the solid composition can only be used at a low speed under low load. Further, since the addition of PTFE will decrease mechanical strength such as impact resistance, the composition finds limited applications.
Accordingly, it is desirable to provide a sliding material composition comprising PPS with good abrasion resistance and also good mechanical strength including impact strength.
In general, to improve impact strength of a resin, a flexible polymer is blended with the resin. However, when an elastomer, for example, is blended with the resin, abrasion characteristics and lubricating properties deteriorate and no desirable composition is achieved.